为了综合比较单双脉冲激光诱导击穿光谱技术(LIBS)在液体中重金属元素的检测效果, 利用自建的液相射流单-双脉冲LIBS技术装置, 对AlCl3水溶液中的Al元素LIBS特性进行测量和分析。 实验中使用两台532 nm Nd∶YAG激光器作为激发光源, 等离子体辐射信号通过光谱仪和ICCD进行采集。 实验研究了单脉冲下Al(396.15 nm)发射谱线的谱线强度随激光能量、 ICCD门延时、 门宽之间的变化关系, 获得了最优化实验参数激光能量为50 mJ, ICCD门延迟为1 200 ns, 门宽为150 ns。 在相同的实验条件下, 实验考察了Al(369.15 nm)发射谱线的谱线强度随双脉冲之间的延时, 激光总能量, ICCD门延时的变化关系, 获得了最优化实验参数为两双脉冲之间的延时为1 000 ns, 激光总能量为50 mJ, ICCD门延时为1 100 ns。 单脉冲和双脉冲条件下获得重金属Al的LIBS检测限分别为26.79和10.80 ppm, 双脉冲LIBS技术使元素检测限下降2倍多。 实验结果表明双脉冲可以提升LIBS技术的探测灵敏度, 为LIBS技术应用于水体中重金属快速检测提供了依据。

A homemade experimental setup of laser-induced breakdown spectroscopy (LIBS) with aqueous jets was used to compare the detection results of dual-pulse (DP-LIBS) and single-pulse laser-induced breakdown spectroscopy (SP-LIBS) for heavy metal elements in liquids. Two Q-switched Nd∶YAG lasers that operated at 532 nm were utilized to generate plasma on the AlCl3 aqueous jets. The plasma emission signal was detected by spectrometer with an intensified charge-coupled device (ICCD). The effects of laser-pulse energy, ICCD gate width, and ICCD gate delay on the intensity of the Al spectral line at 396.15 nm were presented for SP-LIBS. Experimental results showed the optimum parameters for laser energy, ICCD gate width, and gate delay were 50 mJ, 150 ns, 1 200 ns, respectively. The influence of experimental parameters, including interpulse delay, total pulse energy, and ICCD gate delay on the signal enhancement of the Al 396.15 nm spectral line intensity was investigated and optimized. Results showed that the optimal parameters for interpulse delay, total pulse energy, and ICCD gate delay were 1 000 ns, 50 mJ, 1 100 ns respectively. The detection limits of Al were 26.79 and 10.80 ppm by SP-LIBS and DP-LIBS, respectively. The results indicated that DP-LIBS can improve the detection sensitivity which offers a feasible basis for the detection of metallic elements in liquid.